Anti-Stokes Laser Cooling in Bulk Erbium-Doped Materials

We report the first observation of anti-Stokes laser-induced cooling in the ${\mathrm{Er}}^{3+}:{\mathrm{KPb}}_2{\mathrm{Cl}}_5$ crystal and in the ${\mathrm{Er}}^{3+}:\mathrm{CNBZn}$ (${\mathrm{CdF}}_2\mathrm{\text{−}}{\mathrm{CdCl}}_2\mathrm{\text{−}}\mathrm{NaF}\mathrm{\text{−}}{\mathrm{BaF}}_2\mathrm{\text{−}}{\mathrm{BaCl}}_2\mathrm{\text{−}}{\mathrm{ZnF}}_2$) glass. The internal cooling efficiencies have been calculated by using photothermal deflection spectroscopy. Thermal scans acquired with an infrared thermal camera proved the bulk cooling capability of the studied samples. The implications of these results are discussed.

Figure 1

(a) Signal deflection amplitude normalized by the sample absorption as a function of pumping wavelength for the ${\mathrm{Er}}^{3+}:{\mathrm{KPb}}_2{\mathrm{Cl}}_5$ crystal. (b) Phase of the photothermal deflection signal as a function of pumping wavelength. (c) Photothermal deflection signal waveforms in the heating (800 nm) and cooling (870 nm) regions and around the cooling threshold (850 nm).

Figure 2

(a) Signal deflection amplitude normalized by the sample absorption as a function of pumping wavelength for the ${\mathrm{Er}}^{3+}:\mathrm{CNBZn}$ glass. (b) Phase of the photothermal deflection signal as a function of pumping wavelength. (c) Photothermal deflection signal waveforms in the heating (808 nm) and cooling (860 nm) regions.

Figure 3

Time evolution of the average temperature of the ${\mathrm{Er}}^{3+}:{\mathrm{KPb}}_2{\mathrm{Cl}}_5$ at 870 nm. The insets show colormaps of the temperature field of the whole system (sample plus cryostat) at two different times as measured with the thermal camera. The rectangle in the upper inset delimits the area used for calculating the average temperature of the sample.

Figure 4

Time evolution of the average temperature of the ${\mathrm{Er}}^{3+}:\mathrm{CNBZn}$ at 860 nm. The insets show colormaps of the temperature field of the whole system (sample plus cryostat) at two different times as measured with the thermal camera. The rectangle in the upper inset delimits the area used for calculating the average temperature of the sample.